1. Field of the Invention
Embodiments of the invention relate to a liquid crystal display device, and more particularly, to a liquid crystal display device that allows effective visual inspections of a sealant and prevents defect generations in a sealant.
2. Discussion of the Related Art
Cathode Ray Tubes (CRTs), which are traditionally utilized as information display devices, have advantages in functions and cost, but have disadvantages in size miniaturization and portability. On the other hand, recent advancement in semiconductor technology has allowed liquid crystal display (LCD) devices to have better functions. In particular, LCD devices advantageously become smaller and lighter and consume low power, and accordingly receive attentions as replacement for overcoming the disadvantages of the CRTs. Thus, the LCD devices have gradually replaced CRTs and increasingly become as the preferred display device for information processing equipment in the recent times.
Generally, an LCD device includes a lower substrate having a thin film transistor and a pixel electrode thereon, an upper substrate having a color filter layer of red (R), green (G) and glue (B) colors thereon, and a liquid crystal layer interposed between the lower and upper substrates. Upon fabricating a liquid crystal panel by boning the lower and upper substrates, driving signal, e.g., gate signal, and data signal are applied to the liquid crystal panel region to generate an electric field on the pixel electrode, and the generated electric field twists liquid crystal molecules to adjust transmissivity of light emitted from a backlight, thereby implementing (displaying) images.
FIG. 1 is a plane view schematic diagram illustrating an LCD device according to the related art. As shown in FIG. 1, a plurality of gate lines 24 are arranged to cross a plurality of data lines 25 in a perpendicular manner on a lower substrate 10, thereby defining a plurality of pixel regions. A pixel electrode 23 is arranged in each of the plurality of pixel regions. A thin film transistor (TFT) which is a switching device is arranged at each intersection between the gate lines 24 and the data lines 25. Also, a gate pad 24a and a data pad 25a are electrically connected to one of the ends of the gate lines 24 and the data lines 25, respectively, to receive applied driving signal and data signal generated from a printed circuit board.
An upper substrate 40 has a common electrode (not shown) arranged at a region corresponding to an active region 21 of the LCD device and overlapping the pixel electrode. The common electrode receives a common voltage applied from an exterior via a common voltage line 30. The lower substrate 10 and the upper substrate 40 are bonded at their edges with a sealant 50.
FIG. 2 is an exploded view schematic diagram of region A shown in FIG. 1. As shown in FIG. 2, the sealant 50 is printed on the region on which the common voltage line 30 is located to form seal lines (shown by dashed lines). The sealant 50, which is used to bond the lower substrate 10 and the upper substrate 40, overlaps the common voltage line 30 (shown as shaded).
FIG. 3 is a cross-sectional view schematic diagram along I-I′ of FIG. 1. As shown in FIG. 3, the common voltage line 30 is formed on the lower substrate 10. The sealant 50 is coated on the common voltage line 30 to bond the lower substrate 10 and the upper substrate 40 together. The sealant 50 contains conductive balls 56. The conductive balls 56 come in contact with the common voltage line 30 on the lower substrate 10 and the common electrode 44 on the upper substrate 40 and supply a common voltage signal applied to the common voltage line 30 to E the common electrode 44.
As such, the LCD device according to the related art employs the conductive balls 56 in the sealant 50 to supply the common voltage signal to the common electrode 44 on the upper substrate 40. Thus, the sealant 50 needs to overlap the common voltage line 30. However, the LCD device having such a structure may encounter the following problems.
An LCD device commonly undergoes an inspection for determining whether production defects are presented. The inspection commonly is performed not only in each production process but after the completion of the production process of the LCD device. Thus, the inspection of the sealant of the LCD device is performed not only at the sealant printing process but after the completion of the production process of the LCD device. During the inspection of the sealant at the sealant printing process, an assessment is made as to whether a preset amount of a sealant material has been printed.
In addition, the inspection of the sealant after the completion of the production process of the LCD device is performed on the sealant as it bonds the lower substrate 10 and the upper substrate 40 together. Thus, such an inspection of the sealant after the completion of the LCD production process is performed by a visual inspection. For example, the sealant is visually observed to inspect whether a line width of the sealant is non-uniform, whether the sealant has a crack or whether the sealant is partially separated.
However, the LCD device according to the related art employs the conductive balls in the sealant and has the sealant overlap the common voltage line. As a result, a visual inspection cannot be performed effectively on the sealant after the completion of the LCD production process due to the common voltage line formed of an opaque metal and the overlap between the common voltage line and the sealant.